Our practice is that you can pick your own consistent start time between 7-9. You can also do things like compress your week to 4 10 hour days or add an hour to get a day every two weeks. We don't want you in the office after 6 on anything approaching a regular basis. You can vary the time by day, which is common for childcare or other outside demands on your time.
If your habit is a 5 hour start window for an 8 hour workday, you're not going to work out.